Parachute

Many objections were made to the form of Cocking's para chute; but there is little doubt that had it been constructed of sufficient strength, and perhaps of somewhat larger size, it would have answered its purpose. John Wise (1808-79), the American aeronaut, made some experiments on parachutes of both forms (Garnerin's and Cocking's), and found that the latter always were much more steady, descending generally in a spiral curve.

The Modern Parachute.

In modern aviation, parachutes are recognized as a part of the standard flying equipment for use with aeroplanes. In 1912 Capt. Berry made the first descent from an aeroplane at St. Louis, Mo. He used a medium sized parachute, folded and stuffed into a conical cylinder tied under the front end of the aeroplane skid. During the last days of the World War in 1918, German aviators frequently used them; but after the war little was done to complete the use of parachutes until about the year 1921. At this time British and American aviators began working upon a parachute that could be carried con veniently by a pilot. It was obvious that the old style balloon parachutes were too cumbersome to carry in aeroplanes.

The Seat Pack and Lap Pack.

In 1918 the U.S. Army Air Service experimented with a "seat pack" type of parachute and in 1919 the type was generally recognized as standard and ex tremely efficient. More than 1,500 experimental jumps were made in achieving perfection. The "seat pack" is used as a seat cushion, thus removing all weight and bulk from the person of the aviator, and is the type in most general use for pilots. The "lap pack" has been developed for the use of machine gunners and photogra phers, or where it is not desirable to use a "seat pack." It will be readily understood that an aerial machine gunner usually has the most room directly in front of him and below the waist line. There is also the pack which is strapped on the back and which is used for special cases.

The standard seat pack aeroplane parachute is folded into a compact pack about the size of an ordinary chair cushion, but about twice as thick. It is worn strapped upon the body with the pack in place beneath the buttock of the wearer and it be comes the cushion when the aviator takes his seat in an aeroplane. Thus, the regular cushion in aeroplane cockpits is generally omitted. The equipment weighs approximately 18 lb. The sail of the parachute is made of carefully chosen untreated silk, because untreated silk does not become creased so easily as the finished material. When spread open, the parachute is 22, 24 or 28 ft. in diameter, 24 ft. being standard. The shroud lines are made from high-grade thrown silk and consist of not less than 32 threads of three-ply, each with a breaking strength of not less than pounds. The main parachute is pulled from its case by a smaller "pilot chute," about 3 ft. in diameter, which operates by spring when the aviator pulls the "rip cord" that holds the pack closed. When open the parachute descends at the rate of 16 to 24 ft. per second, depending upon the weight of the wearer and density of the air. Each parachute is tested by an actual drop from an aircraft using a dummy or weight.

The lowest height at which a parachute will open is probably not less than 15o ft., although a few forced jumps have been made at slightly lower altitudes. The lowest altitude considered safe is 25o ft., although the higher the jumper is, the better are his chances, because sometimes delayed openings occur. Jumps have been made from aeroplanes as high as 25,000 ft.

Use of Parachute.—There are two general ways to leave an aircraft with a free-type manually-operated parachute ; one is by the "lift off" method, and the other by the "free fall" method. In making a lift off jump, the jumper gets on one of the wings where there are no projections or obstructions of any kind directly behind, and pulls the rip cord, which opens the parachute and pulls the jumper from the aircraft. In case of jumps made for training purposes, this method eliminates unnecessary hazards and gives the student a better chance to become familiar with parachute operation. In making a free fall, the jumper clears

the aircraft at any point, free of obstruction, that is convenient to him. After falling clear, a jerk on the rip cord releases the parachute. Where there is plenty of altitude, a long "free fall" is not dangerous. Actual jumps have disproven the theory that a man falling free through space becomes confused and forgets to pull the rip cord. Several cases are on record where men have fallen 3,00o to 4,00o ft. without pulling the rip cord and yet retained perfect control of their senses. When the parachute is opened and descending at its normal rate, the jumper's position in the harness is as though he were sitting in a swing. The rate of descent is between 16 and 24 ft. per second depending on the weight of the wearer, the size of the parachute and the density of the air. The impact on landing at these speeds is equivalent to that obtained from a free jump from heights of 4 to 9 ft. respectively. In the descent any tendency to oscillate should be checked as soon as possible. This can be done by pulling down vigorously on the shroud lines on the high side of the parachute as the body swings in that direction. The instant the body starts on the return swing, the shroud lines should be released and the swing met by pulling down on the opposite shroud lines. At the same time the jumper should try to face the line of flight, as a much better and safer landing can be effected in that position. This can be done by grasping a handfull of shroud lines, and giving a vigorous swing on them, not down, but as much in a circle as possible. This tends to "spin" the parachute around. During descent, if it is seen that there is danger of striking some building or other obstructions, it is possible to change the gliding angle by pulling down on the shroud lines. This tends to spill air from under the parachute on the higher side, and results in an appreciable angle of glide toward the lower side. This should never be attempted when near the ground, except in an emergency, as it results in an increased rate of descent.

If it should be seen that the parachute is going to "under shoot" the place where it is desired to make the landing—that is, the parachute in its normal flight is gliding toward a desired landing place, but its rate of descent is such that it evidently will reach the ground before this spot is reached—nothing can be gained by trying to "side slip" in this direction for the parachute will travel further in a horizontal direction if it is kept stable. Upon nearing the ground the best method of relieving the shock of impact is to grasp the harness webbing over the head, retaining the sitting position in the harness—but with the knees slightly lower than the hips, with feet together and lifted slightly up and forward—relaxing the muscles as in jumping off a low platform. The body should be lifted up into the harness by pulling on the harness webbing just before the moment of striking. If the parachute has a tendency to "fill out" and drag the body along the ground on landing, it can be collapsed by pulling the top shroud lines toward the body, which tends to straighten the para chute out in the form of a sheet. Pulling on the lower shroud lines will have a tendency to keep the parachute "filled out." In case it is seen that a landing is going to be made in a body of water, it is best to settle well back into the harness and unsnap the leg straps; when close to water (about 12 ft.) unsnap the breast snap ; and when 4 or 5 ft. from the water, drop out of the harness.

Parachute Flare.

A parachute flare contains illuminating chemicals attached to a small parachute, which, when ignited and dropped from an aircraft, will descend slowly and light up the countryside for many miles. Parachute flares are used for military purposes to discover night movements of enemy troops by aerial observers; by aviators to locate landing fields at night, guide the approach to the earth and to take night photographs.